We consider whether Barabási multiclass priority service queueing models are appropriate for modelling voice and short message service interusage and voice usage residual time distributions for a set of high usage subscribers of an Asian telecommunication service provider. We find that a model with a non priority service discipline rather than any priority discipline provides an alternative explanation for the fitted power-law for the interusage time distributions. We also find that a Barabási model provides an alternative explanation to the fitted power-law for the voice usage residual time distribution. However, the exponent of the fitted power-law has not been observed before. Therefore, we propose and analyse a new Barabási list-of-tasks priority model with time varying and discrete task priorities. For a special case we show that the waiting time distribution has a power-law with a previously unknown power-law decay exponent, which is different from the observed exponent for the voice usage residual time distribution.